Process for the manufacture of hose or tubing with a high resistance to pressure and fatigue

Abstract

A process for the manufacture of hose or tubing conditions plastic high pressure hose having at least one reinforcing layer of steel wires, cords or longitudinal segments thereof. The hose is internally pressurized for a predetermined period of time which provides a residual permanent elongation of at least 0.5% and increases the interior volume by at least 2% upon release of the pressure.

We claim: 
     
       1. A process for conditioning a plastic high pressure hose comprising the steps of providing in its wall at least one reinforcing layer of steel wires or cords having an elongation at rupture in the range of 4.5% to 6%, internally pressurizing the hose for a predetermined time interval which pressure is released thereafter and wherein, due to this temporary application of internal pressure, the wires, cords or longitudinal segments thereof in the inner reinforcing layer or layers in the hose receive a residual permanent elongation of at least 0.5% and whereby the interior volume of the hose is increased by at least 2% after release of said pressure. 
     
     
       2. Process according to claim 1, wherein the interior volume is transitorily increased by at least 6%. 
     
     
       3. Process according to claim 1, wherein the applied internal pressure is at least 90% of the burst pressure of the hose. 
     
     
       4. Process according to claim 1, wherein the time interval for applying internal pressure is between 0.1 and 65 sec.. 
     
     
       5. A process for conditioning steel wire reinforced plastic high pressure hose and the like, comprising: selecting a steel wire reinforced plastic high pressure hose comprising at least one innermost reinforcing layer, said layer comprising steel wires or cords having an elongation at rupture in the range of 4.5% to 6%,   internally pressurizing the hose for a predetermined time interval, and   providing a residual permanent elongation of at least 0.5% and increasing the interior volume of the hose by at least 2% upon release of the pressure.   
     
     
       6. A process according to claim 5, wherein the interior volume is transitorily increased by at least 6%. 
     
     
       7. A process according to claim 5, wherein the applied internal pressure is at least 90% of the burst pressure of the hose. 
     
     
       8. A process according to claim 6, wherein the applied internal pressure is at least 90% of the burst pressure of the hose. 
     
     
       9. A process according to claim 5, wherein the time interval for applying internal pressure is betwen 0.1 and 65 seconds.